Method of treating a surface with a stable aqueous silanol dispersion



United States Patent 3,154,431 METHOD OF TREATING A SURFACE WITH ASTABLE AQUEOUS SILANOL DISPERSION Thomas R. Santelli, Toledo, Ohio,assignor, by mesne assignments, to J ohns-Manville Fiber Glass Inc.,Cleveland, Ohio, a corporation of Delaware No Drawing. Continuation ofapplication Ser. No. 279,960, Apr. 1, 1952. This application Oct. 16,1957, Ser. No. 690,427

4 Claims. (Cl. 117-161) This invention relates to the production ofstable aqueous silanol dispersions. More particularly the inventionrelates to the production of stable aqueous silanol dispersions byhydrolyzing selected silanes in buttered aqueous solutions.

This application is a continuation of my copending application SerialNo. 279,960, filed April 1, 1952, now abandoned.

One of the greatest impediments to the commercialization ot silanols asWater and heat resistant coatings is that they have not been availablein the form of stable aqueous solutions or dispersions. Attempts toproduce aqueous silanols heretofore, such as by neutralization ofaqueous alkaline siliconates, have resulted in the formation ofpolymeric silanols which precipitated from the aqueous phasesubstantially as rapidly as they were formed. Therefore, it has beencustomary .to apply the alkaline siliconates per se to render materialswater repellent.

Use of these materials, however, is undesirable because of thesubstantial proportion of associated alkali which is highly corrosive.Where the corrosiveness can not be tolerated the alkali must be removedby washing or other equally expensive and time consuming process step.

There is therefore an important need for silanols in stable aqueoussolution or dispersion for large volume, low-cost operations. This needis especially important where small quantities of silanol per squarefoot are to be applied to the material to be, treated.

Aqueous solutions of silanols are also desirable because materials whichrequire treatment to be rendered water repellent are generally readilywet by water and it is this ease of wetting that is the occasion fortreatment to impart water repellency to the material.

It is accordingly an important object of this invention to provide amethod for the production of stable aqueous dispersions of silanols.

It is a further object to provide a method for the production of stableaqueous dispersions of silanols wherein selected silanes are hydrolyzedin buttered aqueous solutions.

A still further object is to provide a method for the production ofstable aqueous dispersions of organo silanols by hydrolyzing selectedorgano silanes in buffered aqueous solutions.

The present invention is based upon the discovery that by proceeding inan unorthodox manner it is possible to obtain a substantially neutralsolution which is a stable aqueous dispersion of a silanol.

In accordance with the present invention stable aqueous dispersion of asilanol is prepared by adding a selected hydrolyzable silane to anaqueous solution of a selected butter. The amount of buffer employedwill be sufiicient to retain the pH of the resulting dispersion between3 and 8.

The procedure for the production of a stable aqueous silanol dispersionin accordance with the present invention comprises adding thehydrolyzable silane to a previosuly prepared aqueous solution of abutter. The rate of addition of the silane may be as rapid as isconsistent with temperature control.

It is desirable to use a large excess of water over that which isrequired to hydrolyze the silane, to avoid gellation. Such a largeamount of water need not be present during the hydrolysis however.Instead it may be added after hydrolysis to dilute the silane dispersionto a desired concentration. However, the amount of water used forhydrolysis should be great enough so that the aqueous phase of theresulting dispersion prior to further dilution is at least from about toabout of the dispersion. The water used for hydrolysis may be retainedat ordinary temperatures, i.e., about 10 to 40 C., but it is preferredthat it be maintained at about 5 to 10 C.

In the hydrolysis of a silane by the present method, the butter isemployed to prevent the pH of the aqueous phase from dropping below 3,which normally occurs during hydrolysis of halogenated silanes becauseof the formation of hydrogen halide as the halide atoms attached tosilicon are replaced by hydroxy groups.

At a pH below 3, as has been the experience of the prior art, thesilanol formed would condense and precipitate from the aqueous phase.Accordingly buffers are employed which are effective to sustain the 3 to8 pH range.

'Iwo indicators should be used during the hydrolysis so that the ratesof addition can be control-led to prevent the pH during the hydrolysisfrom going below 3 or above 8. The pH is usually maintained at about 6.8to 7.5 during th hydrolysis.

It is preferred that the proportion of buffer in the aqueous hydrolysismedium be sufficient to take up the halogen atoms as they are released[from the halosilane during hydrolysis. Thus for example, when sodiumacetate is employed as the butter, sodium chloride will be formed in theaqueous phase. concomitantly acetic acid will be formed. However, sinceacetic is a weak acid the pH of the system will be retained in the rangebetween 3 and 8. This pH range is considered to be substantially neutralsince it permits the silanol .formed to remain in the highly dispersedphase without precipitation.

It is preferable to adjust the pH of a dilute silanol dispersionproduced by the method of the invention between about 4 and about 7, andmore desirable between about 5 and about 6. Such a composition is stablein such pH range as evidenced by a lack of gel particles in thedilutedispersion when it is permitted to stand before being used.

The stability of a silanol dispersion produced by the method of theinvent-ion may be from one hour to several days to two weeks dependingon the particular silanol, concentration of silanol, pH, temperature,etc.

The product of invention is a silanol having an average unit structurecorresponding to the formula nmsnorono (4 (mv +n wherein m is a numberfrom .05 to 3; n is a number from 1 to 3.95; the sum of mv+n is from 2to 4; v is the average valence of the group R; and the groups R areorganic groups having from one to twelve carbon atoms, as hereinbeioredefined.

The term monomeric silanol is used herein to mean a substance whosemolecule contains one silicon atom to which from one to three hydroxygroups are attached, or two to three such silicon atoms which areconnected by divalent organic groups, the remaining free valences of thesilicon atom(s) being attached by linkages to monovalent organic groups.Thus, v in the above general formula is a number from 1 to 2.

Silanols produced by the present method may be partially condensed,i.e., may contain some polymeric molecules which can be considered to bederived by condensation between hydroxy groups attached to silicon atomsin two or more molecules of monomeric silanols, with the formation ofS1OSi l l linkages. Thus, the letter n in the formula for the averageunit structure of a silanol produced in the method of the inventionindicates the average degree of condensation in the silanol molecules.It is believed, however, that in at least part of the molecules of sucha silanol :1 equals 4-mv, i.e., that at least part of the silanolmolecules remain in monomeric form. The fact that a silanol produced inthe practice of the invention is capable of being dispersed in aqueousmedium, indicates that the silanol molecules are of very low averagemolecular weight.

Silanes applicable for use as starting materials in the present methodinclude those corresponding to the general formulae wherein R is anorganic group containing from 1 to 12 carbon atoms inclusive; w is aninteger from 1 to 3 inclusive; X is chlorine, bromine or fluorine; Z isR or X; and y is an integer from 1 to 2.

The silane starting material may be present separately I or inadmixture.

The ratio of R groups to silicon atoms in the silane (R/Si ratio) may bein the range between 0.05 to 3 and will preferably be in the range from0.05 to 1.25.

It is preferred that a monovalent organic group attached to silicon atomin a hydrolyzable silane that is an alkenyl group be analpha-beta-unsaturated group such as a vinyl group.Beta-gamma-unsaturated groups in alkenyl silanes, particularly methallylgroups in methallylsilanes, tend to be highly unstable duringhydrolysis. Thus, these groups, like beta-halo-substituted propyl andbutyl groups, may be considered to be hydrolyzable groups in thepractice of the invention, since such groups are removed from silanestarting materials during hydrolysis.

Examples of hydrolyzable organo-substituted halosilanes that may be usedin the practice of the present invention include: alkylsilanes such asmethyltrichlorosilane, methyltribromosilane, methyltrifiuorosilane,ethyltrifluorosilane, diethyldifluorosilane, ethyltrichlorosilane,diethylethoxychlorosilane, ethyldiethoxychlorosilane, 1-propyltrichlorosilane, l-propyltrifiuorosilane, dipropyldichlorosilane,l-butyltrichlorosilane, isobutyltrichlorosil ane, dibutyldifluorosilane,l-pentyltrichlorosilane, isoamyltrichlorosilane,l-pentyltrifluorosilane, di-l-pentyldifiuorosilane,l-hexyltrichlorosilane, l-heptyltrichlorosilane, 1-octyltrichlorosilane,l-decyltrichlorosilane, l-dodecyltrichlorosilane,alpha-chloroethyltrichlorosilane, alpha-chloropropyltrichlorosilane,gamma-chloropropyltrichlorosilane, alpha-chlorobutyltrichlorosilane,isopropyltrichlorosilane, tertiary hexyltrichlorosilanes, secondarybutyltrichlorosilane, secondary amyltrichlorosilanes, secondaryhexyltrichlorosilanes, secondary octyltrichlorosilanes, and secondarynonyltrichlorosilanes; alkenylsilanes such as vinyltrichlorosilane;arylsilanes such as phenyltrichlorosilane,

A a-naphthyltrichlorosilane, phenyltrifluorosilane,diphenyldichlorosilane, p-chlorophenyltrichlorosilane,p-tolyltrichlorosilane and phenylmethyldichlorosilane; aralkylsilanessuch as beta-tolylbutyltrichlorosilanes,beta-tolylpropyltrichlorosilanes, beta-tolylisobutyltrichlorosilanes,benzyltrichlorosilane, beta phenylethyltrichlorosilane,betatolylethyltrichlorosilanes, beta phenylpropyltrichlorosilane, gammaphenylpropyltrichlorosilane, beta (chlorophenyl ethyltrichlorosilanes,beta- (trichlorophenyl ethyltrichlorosilanes, beta(dichlorophenyl)ethyldichlorosilanes,beta-(dichlorophenyl)propyltrichlorosilanes,alphaphenylethyltrichlorosilane, alpha tolylethyltrichlorosilanes andalpha-(chlorophenyl)-ethyltrichlorosilanes; and cycloaliphaticsilanessuch as cyclohexyltrichlorosilane, cyclohexylmethyldichlorosilane,trimethylcyclohexyltrichlorosilanes andp-tertiary-amylcyclohexyltrichlorosilane.

Examples of cross-linked organosilanes that may be present in ahydrolyzable silane composition used in the practice of the inventioninclude: bis(trichlorosilyl)- isobutanes, tri(dichlorosilylmethylene),trichlorosilylmethyltrichlorosilane, 1,2-bis(trichlorosilyl)ethane, bis-(trichlorosilyl)benzenes, trichlorosilylethylcyclohexyltrichlorosilane,1,6-bis(trichlorosilyl)hexane,1,6-bis-(trichlorosilyl)-2,5-dimethylhexane and 1,3 bis(trichlorosilyl)-propane.

The preferred silanes to be used in the practice of the inventioninclude monorganoand diorgano-substituted silanes in which the organicgroups contain from one to six carbon atoms. When the organic groupsconsist of alkyl groups, it is preferred that they be primary orsecondary alkyl groups, and it is desirable that they be primary orsecondary alkyl groups having from two to four carbon atoms.

Buifers applicable to use in the present invention include metalcompounds, other than hydroxides, which are capable of taking up thehalogen liberated from the silane during hydrolysis. Buffer compoundsmay be defined as compounds which react with an acid to replace the acidhydrogen atom with the metal cation of the butter, thereby forming themetal salt of such acid.

It is to be understood that the buffer employed in the present inventionare in fact metal bases, other than hydroxides, with respect to thehydrogen halide that is formed during the hydrolysis. In other words,the buffer is a compound which releases its cation to replace thehydrogen of the hydrogen halide by-product.

Such a compound is the substitution product of a sub stance with'alabile hydrogen atom, having a dissociation constant (for the hydrogen)at least as small as about 1.l 10 in which the labile hydrogen atom hasbeen replaced by a valence of any metal which is capable of forming achloride, aroxylate, or acylate salt, e.g., an alkali metal (i.e.,sodium or potassium), an alkaline earth metal (i.e., calcium, barium orstrontium) or lead, zinc or magnesium. In other words, in order that acompound of such a metal may be basic, it must be a compound of such ametal with a substance having a dissociation constant (for the labilehydrogen atom) equal to or less than that of phosphoric acid.

The most common examples of such metal bases include the borates,carbonates, alcoholates (such as the methoxides and ethoxides),bicarbonates, citrates, phosphates and acetates of such metals,particularly of the alkali metals.

. The following'examples illustrate the practice of the invention:

EXAMPLE 1 An aqueous silanol dispersion is produced by the method of theinvention by the following procedure:

(a) A buffer (10.14 grams of sodium bicarbonate) is mixed with Water (55grams) and the solution is placed in a 2,000 ml. three-necked roundbottom flask equipped with a stirrer and a dropping funnel. Anorganosilane (6 grams of methyltrichlorosilane) is placed in the drop--ping funnel and is added to the flask dropwise with stir-- ring over aperiod of about two minutes. When the addition is complete, the mixturein the flask is poured into water (1,000 grams).

([1) The procedure described in (a) is repeated, except that the amountof sodium bicarbonate used is 7.56 grams, and the organosilane used isdimethyldichloro' silane (6 grams).

(0) The procedure described in (a) is repeated, except that the amountof sodium bicarbonate used is 4.62 grams, and the organosilane used istrimethylchlorosilane (6 grams).

(:1) The procedure described in (a) is repeated, except that the amountof sodium bicarbonate used is 9.07 grams, and the organosilane used isethyltrichlorosilane (6 grams).

(2) The procedure described in (a) is repeated, except that the amountof sodium bicarbonate used is 6.38 grams, and the organosilane used isdimethylchlorosilane (6 grams).

(f) The procedure described in (a) is repeated, except that the amountof sodium bicarbonate used is 4.12 grams, and the organosilane used isdiethylchlorosilane (6 grams).

(g) The procedure described in (a) is repeated, except that the amountof sodium bicarbonate used is 8.32 grams, and the organosilane used ispropyltrichlorosilane (6 grams).

(h) The procedure described in (a) is repeated, except that the amountof sodium bicarbonate used is 7.31 grams, and the organosilane used is asec.-amyltrichlorosilane (6 grams), prepared as follows: A mixture ofpentenes (1.19 mols, comprising a high percentage of Z-pentene) andsilicochloroform (1 mol) is pumped into an opening at the bottom of areactor which consists of a vertical tube approximately twenty inches inlength, having an internal diameter of about five inches. The length ofthe reactor is surrounded by electrically heated coils, covered withasbestos packing, which maintain the temperature in the reactor atapproximately 370 C. The reactants are permitted to remain in thereactor for approximately one hour, during which time the pressureinside the reactor is about 1,000 pounds per square inch gauge. Thereactor is cooled to room temperature, and the products formed areremoved and fractionally distilled through a jacketed column four feetin length packed with glass helices. The products recovered include a 48percent yield (based on pentene) of a sec.- amyltrichlorosilane, B.P.165-170 C. at atmospheric pressure, as well as unreactedsilicochloroforrn and pentenes.

(i) The procedure described in (a) is repeated, except that the amountof sodium bicarbonate used is 7.05 grams, and the organosilane used isphenyltrichlorosilane (6 grams).

(j) The procedure described in (a) is repeated, except that the amountof sodium bicarbonate used is 6.8 grams, and the organosilane used iscyclohexyltrichlorosilane (6 grams).

(k) The procedure described in (a) is repeated, except that the amountof sodium bicarbonate used is 9.32 grams, and the organosilane used isvinyltrichlorosilane (6 grams).

(I) The procedure described in (a) is repeated, except that the amountof sodium bicarbonate used is 7.81 grams and the organosilane used isl-butyltrichlorosilane (6 grams).

(m) A silanol dispersion is prepared by the procedure described in (l)except that the buffer used is sodium carbonate (4.98 grams).

(n) A silanol dispersion is prepared by the procedure described in (1)except that the butter is sodium acetate (7.63 grams).

(0) The procedure described in (a) is repeated, ex cept that theorganosilane used consists of a mixture of l-butyltrichlorosilane (3.99grams) and silicon tetrachloride (2.01 grams), and the amount of sodiumbicarbonate used 'is 9.32 grams.

(p) The procedure described in (a) is repeated, except that theorganosilane used consists of a mixture of l-butyltrichlorosilane (3grams), and silicon tetrachloride (3 grams), and the amount of sodiumbicarbonate used is 9.49 grams.

(q) The procedure described in (a) is repeated, except that theorganosilane used consists of a mixture of l-butyltrichlorosilane (0.3gram) and silicon tetrachloride (5.7 grams), and the amount of sodiumbicarbonate used is 11.8 grams.

A cross-linked silanol dispersion may be prepared as follows:

(r) A cross-linked silane (a bis(trichlorosilyl)isobutane) is preparedaccording to the following procedure:

A carbon steel reactor consisting of a vertical tube approximatelytwenty inches in length, having an internal diameter of five inches, isheated to a temperature of approximately 340 C. by means of electricalheating coils which surround the length of the tube. A mixture ofsilicochloroform (3340 grams) and commerical diisobutylene (1910 gramsof a mixture comprising weight percent of 2,4,4-trimethylpentene-1 and20 percent of 2,4,4-trimethylpentene-2) is pumped into the heatedreactor through an opening in the bottom. When the addi tion, whichrequires a period of about one hour, is com plete, the opening is sealedand the mixture is allowed to remain in the reactor for four hourslonger. During this period the mixture is heated by means of the heatingcoils at temperatures ranging between 320 and 340 degrees C., while thepressure inside the reactor ranges from 1000 to 1200 pounds per squareinch gauge. The heating is then discontinued, and the product isremoved.

The product recovered (4350 grams) is fractionally distilled through anelectrically heated, jacketed glass column four feet in length, packedwith a single-turn glass helices and having a variable reflux head. Theforerun (i.e., material boiling in a range up to about degrees C. at 740mm. Hg) comprises low boiling hydrocarbon gases (which are primarilysaturated hydrocarbons having three or four carbon atoms),silicochloroform (200 grams) and a mixture of the diisobutylene startingmaterials (10 grams). The following materials are recovered aftercollecting the forerun: methallyltrichorosilane (740 grams); a fraction(370 grams) boiling within a range of 148 to 200 degrees C. at 740 mm.Hg, which comprises a mixture of pentyl-, hexylandheptyltrichorosilanes; a fraction (1075 grams) which is a mixture ofoctyltrichlorosilanes, comprising2,4,4-trimethyl-l-pentyltrichlorosilane and2,4,4-trimethyl-3-pentyltrichlorosilane, and abis(trichlorosilyl)isobutane, which is believed to be1,3-bis-(trichlorosilyl)isobutane (1260 grams, 13.1. 225 to 236 degreesC., density at 28 degrees C. compared with that of water at 4 degrees C.(d 1.377, index of refraction at 27 degrees C. (11 1.472). A residue (60grams) remains afiter the distillation.

A bis(trichlorosilyl)isobutane prepared as described above (6 grams) isadded to a solution of sodium bicarbonate (9.32 grams) in water (500grams) by the procedure described in (a) above. When the addition iscomplete, the mixture in the flask is poured into Water (1,000 grams).

(s) The procedure described in the preceding paragraph is repeated,except that a mixture of ethyltrichlorosilane (5.4 grams) and thebis(trichlorosilyl)isobutane (0.6 gram) is used, and the amount ofsodium bicarbonate used is 9.25 grams.

(t) The procedure described in the last paragraph of (r) above isrepeated, except that the bis(trichlorosil3T)- isobutane is firstchlorinated to form a bis(trichlorosilyl)- 2-chloroisobutane (believedto be 1,3-bis(trichlorosilyl)- 2-chloroisobutane). The amount of sodiumbicarbonate used is 8.57 grams.

7 EXAMPLE 2 An aqueous silanol dispersion of the invention is producedby the following procedure:

(a) The procedure described in Example 1(a) is repeated, except that theamount of sodium bicarbonate used is 6.80 grams, and the organosilaneused is l-hexyltrichlorosilane (6 grams).

(b) The procedure described in Example 1(a) is repeated, except that theamount of sodium bicarbonate used is 6.05 grams, and the organosilaneused is l-octyltrichlorosilane (6 grams).

The procedure described in Example 1(a) is repeated, except that theamount of sodium bicarbonate used is 5.54 grams, and the organosilaneused is a mixture of nonyltrichorosilanes (6 grams, comprising mainlysecondary nonyltrichorosilanes).

(d) The procedure described in Example 1(a) is repeated, except that theamount of sodium bicarbonate used is 4.79 grams, and the organosilaneused is l-dodecyltrichlorosilane (6 grams).

(e) The procedure described in Example 1(a) is repeated, except that theamount of sodium bicarbonate used is 6.8 grams, and the organosilaneused is a tert.- hexyltrichlorosilane (6 grams).

EXAMPLE 3 A buffer (9 grams of sodium bicarbonate) is mixed with amixture of water and ice (1500 cc.). To the resulting solution, at atemperature of 10 degrees C. in a 3-liter three-necked flask fitted witha stirrer and a dropping funnel, is added dropwise with stirring over aperiod of above two minutes an organosilane (4 grams ofisobutyltrichlorosilane). The pH of the resulting silanol dispersion is6.8. Raw glass fibers (200 grams) are added to the dispersion. The glassfibers are immediately filtered from the dispersion and washed twicewith the filtrate, and the glass fibers are then weighed to determinethe aqueous silanol dispersion pick-up, which is 350 grams. The treatedfibers are dried at 65 degrees C. The fibers show strong waterrepellency, i.e., drops of water on the fibers can be shaken off withsubstantially no wetting of the surface of the fibers.

EXAMPLE 4 A buffer (30 grams of sodium bicarbonate) is mixed with water(2000 grams) at a temperature of 20 degrees C. To the resulting solutionin the apparatus described in Example 3 is added dropwise with stirringover a period of eight minutes an organosilane (22 grams ofisobutyltrichorosilane). The pH of the resuting silanol dispersion is6.2. Glass botles are then dipped in the silanol dispersion. The treatedglass bottles, after being dried at 65 degrees 0, show strong waterrepellency.

EXAMPLE 5 A buffer (66 grams of sodium bicarbonate) is mixed with water(1200 grams To the desulting solution in the apparatus described inExample 3 is added dropwise with stirring over a period of thirtyminutes an organosilane (50 grams of l-butyltrichlorosilane). Thetemperature of the mixture in the flask is maintained below degrees C.during the addition. The pH of the resulting butylsilanol dispersion is5.6. Samples of cotton poplin cloth (7 in. by 7 in.) are immersed in thesilanol dispersion for one minute. The treated samples are passedthrough a pair of rolls to remove the excess solution, and the samplesare then dried for five minutes at a temperature of 300 degrees F. Aspray rating of 50 to 55 (determined in accordance with Section IV (part5) of the Supplement to Federal Specification CCC-T-l91a, October 8,1945), is obtained on the treated textile samples. Upon washing thetreated samples with water at room temperature (to remove sodiumchloride), the hand of the cloth is soft and full. Furthermore, uponrepeated E3 laundering in hot dilute soap solution and upon repeated drycleaning, the cloth retains its water repellency well.

EXAMPLE 6 Using the procedure and apparatus described in Example 5 ahydrolyzable silane composition (a mixture of 30.64 grams ofl-butyltrichlorosilane and 6.8 grams of silicon tetrachloride) is addeddropwise with stirring over a period of thirty minutes to a solution ofa buffer (53.72 grams of sodium bicarbonate) in water (1000 grams). ThepH of the resulting butylsilanol dispersion is 6.0. Samples of cottonpoplin cloth (7 in. by 7 in.) are immersed in the silanol dispersion forthree minutes. The excess solution is then removed by passing the clothbe tween rolls. The samples are dried for fourteen minutes at atemperature of 300 degrees F. A spray rating of is obtained on thetreated textile samples. Upon washing the treated samples with water atroom temperature (to remove sodium chloride), the hand of the cloth issoft and full, and the spray rating is not appreciably lowered.

EXAMPLE 7 Small rectangular samples of balsa wood are immersed for a fewminutes in the butylsilanol dispersion prepared as described in Example6. The treated pieces of wood are then cured for 45 minutes in an ovenat a temperature of 208 degrees F. Several pieces of the treated wood,along with several pieces of untreated wood, are weighed and are thenweighted down and held immersed under water for fifteen and one-halfhours. At the end of this time, the pieces of wood are again weighed.From the increase in weight of each sample of wood the percent of itsweight in water absorbed is calculated. The treated pieces of woodabsorb 80.5 percent of water, while the untreated pieces absorb 99.5percent of water. (The treated wood absorbs considerably less water whenthe silanol dispersion is more carefully applied so that all the poresof the wood are coated.) Several other samples of the treated wood alongwith samples of the untreated wood are floated on water. After 24 hourseach sample of the treated wood is completely visible, while the samplesof untreated wood are three-quarters submerged, i.e., only one-fourth ofthe upper surface is not covered with water. After 72 hours the treatedpieces are only onehalf submerged, whereas the untreated pieces arecompletely submerged. In the preceding examples, similar good resultsare obtained when the silanols employed are replaced with any of thedilute silanol dispersions prepared as hereinbefore described.Furthermore, any of the other materials hereinbefore described may berendered strongly water repellent by treatment with such silanoldispersions. For example, common red bricks painted with a silanoldispersion produced in accordance with the present method and thenair-dried show excellent water repellency.

Uses

The stable aqeous silanol dispersions produced by the method of theinvention are extremely useful in imparting water repellency to variousmaterials. In fact, one of the most important embodiments of the presentinvention is a method of improving the water repellency of a surfacethat is reactive with a silanol which comprises applying a stableaqueous silanol dispersion produced by the method of the invention, at apH between 3 and 8, to

such a surface.

Such materials will have surfaces which are reactive with the silanoland the principal example of such a surface is having hydroxyl groupstherein whereby a bond between the silanol and the surface is effected.Of such hydroxylated materials that may be treated in accordance withthe present method the most important are siliceous materials andcarbohydrates, including silicates (particuularly magnesium silicate),cellulose, porous ceramic materials, glass, clay, non-carbonaceousmasonry, sand and ores (for flotation). Other materials which may beeffectively rendered water repellent by the present method include woodproducts, paper and mineral fillers (in addition to glass fillers andsilicates) such as clay, mica and talc. The mineral fillers, i.e.,fillers for use in, for example, molding compositions, which may berendered water repellent by silanol dispersions of the invention includeasbestos.

A particularly important application of the present method is thetreatment of glass surfaces including glass fibers, glass cloth, glassbottles, glass plates and the like. The treatment of glass fibers andglass cloth to be subsequently employed in the production of syntheticresin laminates provides improved laminates. Improvement resides in theproduction of high wet strength and a better bond between the glass andresin.

The treatment of any of the above-described materials with an aqueoussilanol dispersion made in accordance with the present method consistssimply in immersing the material to be treated in the aqueous silanoldispersion or applying the dispersion to the material with an ordinarypaint brush until the propontion of silanol adhering to the material iswithin the desired range, as hereinbefore discussed, and then drying thematerial, e.g., by moderate heating or by air-drying. When a silanoldispersion produced by the method of the invention is dried after beingapplied to a material to be treated, condensation of the silanol takesplace to form an insoluble, Water repellent silicone.

I claim:

1. The method of treating a surface which is reactive with a silanol toproduce a coating of insoluble organosilicon compounds thereon, whichcomprises treating said surface with an aqueous dispersion of a silanol,said 10 dispersion having been prepared by hydrolyzing a silane, havinga structure corresponding to the formula Z X F XS]iRS|i-X z Z wherein Ris an organic group containing from 1 to 12 carbon atoms inclusive, X isa member chosen from the group consisting of chlorine, bromine andfluorine and Z is a member chosen from the group consisting of R and X,in an aqueous solution of a metallic salt of an acid having adissociation constant not greater than phosphoric acid, the metallicradical of said salt being chosen from the group consisting of an alkalimetal, an alkaline earth metal, zinc and magnesium, and drying saidsurface at an elevated temperature to cure said silanol.

2. A method as defined in claim 1, wherein the silane is a chlorosilane.

3. A method as defined in claim 1, wherein the buffer is a carbonic acidsalt of an alkali metal.

4. A method as defined in claim 1, wherein the amount of bufier issufficient to retain the pH of the resulting dispersion between 4 and 7.

References Cited in the file of this patent UNITED STATES PATENTS2,390,370 Hyde Dec. 4, 1945 2,426,912 Wright Sept. 2, 1947 2,439,689Hyde Apr. 13, 1948 2,501,525 Krieble et a1. Mar. 21, 1950 2,561,429Sveda July 24, 1951 2,590,812 Barry Mar. 25, 1952 2,600,307 Lucas et a1June 10, 1952 2,624,721 Hatcher et a1 Jan. 6, 1953 2,640,063 Kohl May26, 1953 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PatentNo. 3,154,431 October 27, 1964 Thomas R. Santelli It is hereby certifiedthat error appears in the above numbered patent req'liring correctionand that the said Letters Patent should read as corrected below.

Column 4, line 71, for "(55 grams)" read (500 grams) Signed and sealedthis 10th day of-August 1965.

(SEAL) Attest:

ERNEST W SWIDER EDWARD J. BRENNER Ancsting Officer Commissioner ofPatents

1. THE METHOD OF TREATING A SURFACE WHICH IS REACTIVE WITH A SILANOL TOPRODUCE A COATING OF INSOLUBLE ORGANOSILICON COMPOUNDS THEREON, WHICHCOMPRISES TREATING SAID SURFACE WITH AN AQUEOUS DISPERSION OF A SILANOL,SAID DISPERSION HAVING BEEN PREPARED BY HYDROLYZING A SILANE, HAVING ASTRUCTURE CORRESPONDING TO THE FORMULA